In the hardwood and pine wood industry, planning mills and sawmills generally produce lumbers in the form of elongated boards which are stacked in rows for drying and/or shipping purposes. Generally, these board rows are stacked according to their length, thickness or grade.
When a stack of wood boards is prepared, each layer or row of the stack must have or be close to a predetermined maximum width. Wood boards in a stack may have different dimensions of width and therefore an operator is required to prepare each row or layer of the stack. More particularly, the operator places several wood boards side by side to form a row having a maximum width. If the row of selected wood boards is not close to the maximum width, the operator can substitute one or several wood boards with other boards until the row substantially reaches the maximum allowed width without exceeding it. Alternatively, the operator can simply remove one of the wood boards to form a row having a reduced width. Once the row is completed, it can be stacked on other rows to form a stack. In either case, the productivity decreases: in the first case, the decrease is due to the time lost in handling the pieces of wood while, in the second case, it is due to the fact that the stack contains less wood than possible.
A common practice in this industry is to place rows of longer wood boards underneath the stacks and to place longer boards on both sides of the stacks. Placing the wood boards as such allows the forks of stackers to slide more easily underneath the board rows when handling them and avoid smaller boards to be dropped during the stacker handling. Stacks formed as such are also more solid, the smaller boards being contained within the ‘shell’ formed by longer boards located on the outside of the stack, reducing the chances for the stacks to slump down during transport. This operation of selecting boards for forming rows according to their length after having selected them according to their widths is tedious and is even more time consuming.
Already known in the art are systems for selecting random length wood boards for forming lines of several boards placed end to end having a predetermined length. Also known in the art are systems for sorting and stacking wood boards according to their length for forming groups of boards, each formed by boards of similar length.
The following documents disclose different sorting systems of wood boards: U.S. Pat. Nos. 2,600,147; 2,662,640; 2,762,508; 2,800,225; 2,821,301; 3,006,468; 3,080,969: 3,116,835; 3,203,559; 3,279,600; 3,292,783; 3,343,689; 3,522,880; 3,631,977; 3,889,825; 4,205,751; 4,384,814; 4,892,458; 5,613,827; 5,964,570; 6,016,922; 6,220,423; 6,510,364; 6,598,747; 6,655,902; 7,201,554 and US 200310091421.
None of these systems show how to sort wood boards according to their width for forming rows of boards within a predetermined width range. Neither do they show how to form board rows of constant width further having constant length or longer boards on their sides.
In addition, boards to be stacked in stacks of predetermined width rows are often pre-sorted according to their thickness or grade using different sorting systems. It would be more efficient if this sorting could be made at the same time as the width or length sorting of the boards when forming rows having a predetermined width.
Therefore, there is a need to automate the preparation of rows having a width within a predetermined range in order to increase the productivity and reduce the manual labor costs.
It would also be desirable to further automate the preparation of rows having a width with a predetermined range so that longer boards are placed on each side of a row and so that they form the bottom rows of board stacks.
It would also be desirable to be able to sort boards according to their thickness or grade when forming rows having a predetermined width range.